Reshaping the barn door

[Peter]

Alex,

this is what the PO of my F35 did. As his Autohelm 3000 wheelpilot could not cope with the rudder forces, he installed a trimtab to the trailing edge of the shortened rudder. Then he let the Autohelms motor turn the tab by connecting the ends of the split drive belt to arms on both sides of the top of the tab. He told me he was content with the result. As I already had the Windpilot I ripped off the trimtab and never tried it. When going astern you will get high forces on the tab so you either have to take it off or align it with the rudder by some device. The pendulum rudder of the Windpilot could easily be lifted up 180 degree and be out of the water while not in use or going astern.

Numbknots,

the shortened trailing edge of the rudder was not blunt but somewhat streamlined. The laminating was just poorly done.

Cheers
Peter

[Michel]

At the time I had my F33/35 ck, I looked extensively into trim tab steering and thought of changing the trailing 4" of the rudder into a trim tab. According to self steering literature, trim tabs make for a very slow and delayed steering action. Ant there are the disadvantages with reversing the boat and with linking the trim tab to the steering gear, especially hard on a boat with a traveller running the full width of the transom. I decided against the trim tab at the time and choose a pendulum self steering gear connected to the wheel with a toothed belt on a drum.

[Capitan Sardina]

Very interesting.

I really like the simplicity and feel of a tiller. I have no plans at the present to change the steering system (I have too many projects already), but I would not discard it for the future.

cheers,

alex

[Michel]

Alex,

Don't underestimate the forces on a tiller on the F33/35 catketch. I tried my emergency tiller once under force 5 conditions and soon enough understood why there are two welded lugs on each side of the emergency tiller at the forward end. You can't hold the tiller by hand and really need to rig two tackles to keep the tiller. My wheel with rack and pinion and rod links to the rudder gave a 12:1 reduction in turns and that was not even always enough and certainly too much for an Autohelm 4000 wheelpilot.

How long a tiller do you need to get a 12:1 reduction? If the Center of Effort of the unbalanced rudder is e.g. 0.5 foot behind the rudder stock (I think it's even further aft), you need a 6 foot tiller to have the same 12:1 reduction of force, if my math is right.